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Discussion Starter · #1 · (Edited)
I was able to do some flow simulation testing on a model similar to the thien seperator that I built. I tested two models, one with the intake tangent to the drum, and the other where the intake is through the top with an elbow diverting air flow. The results are kind of interesting. There are more photos in my album.
 

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where's my table saw?
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OK, great!

What are the results as you understand them and do you have any recommendations? :blink:
 

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I'm sure that you did a lot of work to complete the simulation. However what it looks like to an untrained eye is almost what it looked like when one of my kids put three boxes of spaghetti in the washing machine.

I really wish that you would explain the results.
 
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If you look at your velocity legend the Thien separator appears to have more velocity at the inlet and out let which confirms what I experienced after I made a top hat separator as compared to my original Thien. I lost velocity with the top hat. This is one of the reason I built the cyclone separator. The cyclone from my experience is superior to either of the Thiens.
 

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bob willing,
by top hat are you referring to the unit that you place in the DC? And I assume the separator is the type most of us build in a separate container like a 30 gal or 55 gal barrel?

TIA.
Bob
 

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bob willing,
by top hat are you referring to the unit that you place in the DC? And I assume the separator is the type most of us build in a separate container like a 30 gal or 55 gal barrel?

TIA.
Bob
a top hat thien separator looks like this. the innards that facilitate the dust separation sit atop the collector bin, as opposed to a regular separator where the innards sit within the collection bin.
 

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Discussion Starter · #11 ·
Just a couple of observations.
1) I remember seeing a video of a cyclone seperator in operation, and made of clear material. The thing I noticed the most was that the incoming airstream took on a very distinct downward angle just as it entered the barrel. And it didn't matter whether there was material in the air stream or not. This seemed to contradict most references that suggested that the incoming air would be forced to the perimeter, then inward to the outlet, while the heavier material would be drawn down by gravity alone into the cyclone tapered tube. Most refrences simply indicated "an area of turbulence" where the incoming airstream met the revolving airstream and "heavier material dropping due to gravity".
2) My question was then, why does the thien seperator work, with a fair degree of efficiency, and without having to construct the extra height of the taper tube, or add contrivances like helical baffles or inlet extension tubes, or reconfigure the inlet or outlet geometry etc etc. I simply made a baffle for a 55gallon barrel, and have now filled it half dozen times, with only a few cups of dust making it to the shop vac. Thats all. The simulation only took 10 minutes or so to make the computer model, 10minutes to set up the simulation, and a few minutes to run it and get some pretty pictures. And I noticed on the simulation, in following the spagetti strings, that the incoming airstream is immediately "impacted" by the revolving airstream, is forced somewhat up, to the outside, and "a lot of it forced down", "not by gravity but due to pressure", right where the thein baffle slot is located. Hmm. Maybe it's meaningless, but then again, when looking at collectors for seperating grain, for cotton gins, and for sawmills, woodshops, etc, this was never mentioned.
 

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where's my table saw?
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your conclusions...

Would it be safe to say that you think A Thein baffle is more efficient than a cyclone...

You seem to be testing a "top hat" type separator?

Which would be your choice, because of the reduced height over a cyclone, all other things being equal?

Does velocity of air flow out of the "separator" have more effectiveness over volume of air flow?

Would the increased velocity coming out of the vertical stack be a result of a Venturi effect?

Would a reduced velocity in the separator give the particles more time to settle out due to gravity?

Would vanes in the separator help in the separation process.

Is there a way to model this experiment with less "spaghetti" to allow seeing the process more clearly?

Thanks in advance. :yes:
 

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Just a none scientific observation relative to velocity. I noticed on the cyclone that it takes more effort to get the saw dust and shaving out of the barrel (I use a dust pan to scoop out the dust and put it in to bags) the debris is more compacted than before. For example if I have shavings from a forestner bit, TS dust, and planer shavings they are really compacted together.

On my top hat separator I also noticed that large pieces of band saw debris were not being sucked in to the barrel they were still captured within the separator. By debris I mean I take off the hose and suck up some of the small pieces from the band saw table.

Maybe Sawset could run a simulation on a cyclone DC. You could use the dimension from my link in my original thread cyclone DC to do you modeling. Just a thought.
 

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Discussion Starter · #15 · (Edited)
Would the increased velocity coming out of the vertical stack be a result of a Venturi effect?
On the latest images there is less of a velocity change. The sizing overall is also a little more realistic. Well built designs would sort through some of these discrepancies.

Would vanes in the separator help in the separation process.
I remember a study done on industrial cotton gin seperators where helical vanes were tested. Efficiency was reduced in all cases, at least with the way they had it setup.

Is there a way to model this experiment with less "spaghetti" to allow seeing the process more clearly?
Ok. I had time to reconfigure some things. Hopefully now more clear. This time with baffle and realistic sizes closer to the 55gal barrel setup I have. It does have a cone below the baffle though. I'm wondering if it at all matters in this case whether it's a bus, cone or round barrel, since when the barrel is 7/8 full, and still working well, the volume below is lost. And for airflow to get back up to the outlet it would have to pass through the same high speed circulating air around the baffle.
 

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When I get time I'll remove the baffle and run it again for the cyclone DC only.

Don't use the baffle it is not part of the cyclone.


Extend the outlet tube (inside the drum) it needs to be the same length as the upper drum.

One more thing angle the inlet at about 10 degrees down angle as it enters the drum.

The drum and funnel need to be the same length.
 
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